PRACTICAL FILE OF RDBMS

INTRODUCTION TO RDBMS A Relational database management system (RDBMS) is a database management system (DBMS) that is based on the relational model as introduced by E. F. Codd. Most popular commercial and open source databases currently in use are based on the relational model. A short definition of an RDBMS may be a DBMS in which data is stored in the form of tables and the relationship among the data is also stored in the form of tables. Relational databases are powerful because they require few assumptions about how data is related or how it will be extracted from the database. As a result, the same database can be viewed in many different ways. An important feature of relational systems is that a single database can be spread across several tables. This differs from flat-file databases, in which each database is self-contained in a single table. Almost all full-scale database systems are RDBMS's. Small database systems, however, use other designs that provide less flexibility in posing queries. RDBMS data is structured in database tables, fields and records. Each RDBMS table consists of database table rows. Each database table row consists of one or more database table fields. RDBMS store the data into collection of tables, which might be related by common fields (database table columns). RDBMS also provide relational operators to manipulate the data stored into the database tables. Most RDBMS use SQL as database query language. Edgar Codd introduced the relational database model. Many modern DBMS do not conform to the Codd¶s definition of a RDBMS, but nonetheless they are still considered to be RDBMS. The most popular RDBMS are MS SQL Server, DB2, Oracle and MySQL.

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INTRODUCTION TO ORACLE The Oracle Database (commonly referred to as Oracle RDBMS or simply Oracle) consists of a relational database management system (RDBMS) produced and marketed by Oracle Corporation. As of 2008, Oracle had become a major presence in database computing. An Oracle database is a collection of data treated as a unit. The purpose of a database is to store and retrieve related information. A database server is the key to solving the problems of information management. In general, a server reliably manages a large amount of data in a multiuser environment so that many users can concurrently access the same data. All this is accomplished while delivering high performance. A database server also prevents unauthorized access and provides efficient solutions for failure recovery. Oracle Database is the first database designed for enterprise grid computing, the most flexible and cost effective way to manage information and applications. Enterprise grid computing creates large pools of industry-standard, modular storage and servers. With this architecture, each new system can be rapidly provisioned from the pool of components. There is no need for peak workloads, because capacity can be easily added or reallocated from the resource pools as needed. Physical and logical structuring in Oracle An Oracle database system ² identified by an alphanumeric system identifier or SID comprises at least one instance of the application, along with data storage. An instance ² identified persistently by an instantiation number comprises a set of operating-system processes and memory-structures that interact with the storage. Typical processes include PMON (the process monitor) and SMON (the system monitor). Users of Oracle databases refer to the server-side memory-structure as the SGA (System Global Area). The SGA typically holds cache information such as databuffers, SQL commands and user information. In addition to storage, the database consists of online redo logs (which hold transactional history). Processes can in turn archive the online redo logs into archive logs (offline redo logs), which provide the basis (if necessary) for data recovery and for some forms of data replication.

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The Oracle RDBMS stores data logically in the form of tablespaces and physically in the form of data files. Tablespaces can contain various types of memory segments; for example, Data Segments, Index Segments etc. Segments in turn comprise one or more extents. Extents comprise groups of contiguous data blocks. Data blocks form the basic units of data storage. At the physical level, data-files comprise one or more data blocks, where the block size can vary between datafiles. Oracle database management tracks its computer data storage with the help of information stored in the SYSTEM table space. The SYSTEM tablespace contains the data dictionary ² and often (by default) indexes and clusters. (A data dictionary consists of a special collection of tables that contains information about all user-objects in the database). Since version 8i, the Oracle RDBMS also supports "locally managed" tablespaces which can store space management information in bitmaps in their own headers rather than in the SYSTEM tablespace (as happens with the default "dictionary-managed" tablespaces). If the Oracle database administrator has instituted Oracle RAC (Real Application Clusters), then multiple instances, usually on different servers, attach to a central storage array. This scenario offers numerous advantages, most importantly performance, scalability and redundancy. However, support becomes more complex, and many sites do not use RAC. In version 10g, grid computing has introduced shared resources where an instance can use (for example) CPU resources from another node (computer) in the grid. The Oracle DBMS can store and execute stored procedures and functions within itself. PL/SQL (Oracle Corporation's proprietary procedural extension to SQL), or the object-oriented language Java can invoke such code objects and/or provide the programming structures for writing them.

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It is possible to store and retrieve It is possible to store and retrieve large fewer amounts of data in it. requirements. It is less secure. Used for smaller organizations Large organizations where large where security is not major amount data is maintain and security is concern.
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. It is more secure. It reads tables internally. Support null values. It reads data as files internally. It support single user.
2 3 4 5 6 7 8 9
10 11 12
RDBMS It is use to establish relationship concept between two database objects i. 3. tables. No keys are used. Both are used for storage. also important. It requires low software and It requires high software and hardware hardware requirements. present.PRACTICAL FILE OF RDBMS
Difference between RDBMS and DBMS
S. It does not support null values. 2. Examples: FoxPro Examples: SQL Server MS-Access Oracle
Similarities between RDBMS and DBMS 1. Keys are used. Both store data in the form of tables. It is possible to edit record in both DBMS and RDBMS.e.no DBMS 1 There is no relationship concept. 4. amount of data in it. It is easy to retrieve data in both. It support multiuser. No data integrity. Normalization concept is not Normalization is present. Data integrity concept is present.

how the values are processed by the computer. Max 255 bytes. date etc. The various Data Types along with their description are shown below: Data Type char(size) varchar(size) number(size) Date Description Holds fixed-length character string. Max size is specified in parenthesis. with a maximum number of "d" digits to the right of the decimal. Holds variable-length character string.
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. Some data types in SQL are: char. a limited number of such data types come built into a language. Usually. number. and how they are stored. Holds a Date value.
number(size. Size is specified in parenthesis.PRACTICAL FILE OF RDBMS
Data Type A data type is a set of data with values having predefined characteristics. The language usually specifies the range of values for a given data type. Holds Number value with a max number digits specified in parenthesis.d) Holds a Number value with a maximum number of digits of "size" total. Each language has its own data types.

b_no.desg varchar2(10)). It consists of rows and columns. data types have to be mentioned for each field. Syntax: CREATE TABLE table_name (column_name1 data_type. A row represents a single record while a column represents attributes/fields which can be thought of as one of the components contributing to make a record. While creating a table.. SQL Select This statement is used to view data from the table.name varchar2(10). column_name2 data_type.desg. A table can be considered as a basic structure within which data is stored..
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.dept varchar2(10).) Query: create table emp1(e_no number. The above statement creates an empty table (containing no records) named Details having fields-e_no. . Syntax: SELECT column_name(s) FROM table_name Query:To select all the column from the table:select * from studentcse.PRACTICAL FILE OF RDBMS
Create Table With CREATE TABLE. a new table can be created.b_no number.dept.name.

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. Syntax: SELECT column_name(s) FROM table_name WHERE condition Query: select * from studentcse where marks>300. The SQL Select retrieves values from database table which may be repetitive. Thus Where clause is used to specify a selection criterion. we want to retrieve Employee names from database table Employee with salaries above 14000.PRACTICAL FILE OF RDBMS
The Where Clause We might want to retrieve records which satisfy a particular condition. Adding the word Distinct to Select. To do this. Syntax: SELECT DISTINCT column_name(s) FROM table_name Query: select distinct * from studentcse.
The Distinct Keyword Distinct keyword is used to retrieve values that are distinct or non-repetitive. we make use of the clause Where. we can get rid of this problem. For example.

PRACTICAL FILE OF RDBMS
Sorting Sorting is an important feature of any database. Order by Clause ORDER BY is used to get the result in the sorted manner. Syntax: DELETE FROM table_name WHERE column_name = some_value
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.
SQL Delete The SQL delete is used to delete rows from a database table. the order by clause sorts the result in ascending order. We can arrange data according to the sequence we need to put them into. Syntax: SELECT column_name(s) FROM table_name ORDER BY column_name Query: select * from studentcse order by rollno. Unless Explicitly stated.
Query: select * from studentcse order by rollno desc.

DROP TABLE If the user want to delete a table (the table structure.PRACTICAL FILE OF RDBMS
Query: delete from studentcse where rollno=106. attributes.
Query: delete from studentcse where name='Radhika' and marks>300. Query: drop table studentdet. and indexes will also be deleted) Permanently then drop command can be used for the purpose. Syntax: DROP TABLE <table_name>.
Query: delete from studentcse where name like '__n%'.
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.

Syntax: TRUNCATE TABLE <table_name>.PRACTICAL FILE OF RDBMS
TRUNCATE Truncate command is used to simply get rid of the data but not the table itself. Query: truncate table student1.
SQL Update Update statement is used to edit or update data in the table. Syntax: UPDATE table_name SET column_name = new_value WHERE column_name = old_value
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. we might find that there is a need to modify the data. we can use the UPDATE command. Once there's data in the table. To do so.

Tab: This command is used to view all the tables. Query: rename emp to emp2. Syntax: select * from tab. Syntax: select column_name alias_name from table_name.PRACTICAL FILE OF RDBMS
Rename Column Alias are used to rename a table¶s columns for the purpose of a particular query.
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.

Query: describe emp2.
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.PRACTICAL FILE OF RDBMS
Describe: This command is used to describe the structure of the the structure of the table. Syntax: describe tablename.

The various Operators along with their description are shown below in tabular form: Operator Description = > < >= <= <> LIKE AND OR NOT Equal Greater than Less than Greater than or equal to Less than or equal to Not equal to String comparison test Logical And returns TRUE when both the specified conditions are true Logical Or returns TRUE when atleast one of the specified conditions is true Logical Not returns TRUE when none one of the specified conditions is true
Query: select * from studentcse where marks>300. Logical operators (NOT. OR). Comparison Operators ( =.
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. AND. *. -. ). These operators take as input one or more arguments (operands) and return a result. >. <).PRACTICAL FILE OF RDBMS
Logical Operators: Oracle provides a set of built-in operators-Arithmetic Operators (+.

336..PRACTICAL FILE OF RDBMS
Range Searching: SQL In & Between The IN keyword is used to test whether a value(s) is present in the list of values specified after the keyword IN.
The BETWEEN keyword is used to test whether or not a value is present between the two values mentioned in the query followed by the keyword BETWEEN..
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.226.333.
select ename from employee where ecity like 'APS' AND ecode IN(select ecode from company where desg like 'Manager'). Syntax: SELECT column_name FROM table_name WHERE column_name IN ( value1. value2.387).') Query: select * from student where sid in(101. Syntax: SELECT column_name(s) FROM table_name WHERE column_name BETWEEN value1 AND value2 Query: select * from students where rollno between 111 and 113..

AND operator selects a range of data between two values.
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.PRACTICAL FILE OF RDBMS
Not between The NOTBETWEEN .. These values can be numbers. or dates.. Syntax: select * from <table_name> where <column_name> Not between <Range1> and <Range2>. text.

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.
select * from studentcse where name like '__m%'.
select * from studentcse where name like 'A%'.PRACTICAL FILE OF RDBMS
Pattern Matching: The Like Clause: The Like condition can be used to search for a particular pattern in a column in a database table. Syntax: SELECT column_name FROM table_name WHERE column_name LIKE pattern Query: select * from studentcse where name like 'R%' and marks>300.

(ii) MIN (Minimum): It returns the lowest value of a column in a table. (i) AVG (Average): It returns the average value of a column.AGGREGATE FUNCTIONS: Aggregate functions operate against a collection of values. Syntax: SELECT min(column) FROM <table_name>
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.PRACTICAL FILE OF RDBMS
-. Syntax: SELECT avg(column) FROM <table_name>. but return a single value.

NUMERIC FUNCTIONS: Numeric functions are applied on any table having numeric data. Syntax: Select abs(value) from <table_name>
(ii)SQRT (Square root) It is used to find square root of any numeric value. (i) ABS (Absolute): It returns the absolute value of any numeric data.
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. Syntax: Select sqrt(value) from <table_name>. It can also be applied on dual table.PRACTICAL FILE OF RDBMS
-.

power of value) from <table_name>
(iv) ROUND: This function is used to get a rounded figure of a decimal value. Syntax: Select <table_name>. Syntax: Select power(value.PRACTICAL FILE OF RDBMS
(iii) POWER: This numeric function calculates the power of any numeric value. of digits desired after decimal ) from
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. round(value.no.

no. Syntax: Select trunc(value.PRACTICAL FILE OF RDBMS
(v) Trunc: It shows the specified number of digits after truncating the other digits after decimal.
(vi) EXTRACT function: It returns a value extracted from a date or an internal value. of digits desired after decimal) from <table_name>. Syntax: Select extract (<value_name> from µvalue¶) from <table_name>.
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.

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. Syntax: Select ascii(char) from <table_name>. with all letters uppercase.PRACTICAL FILE OF RDBMS
-. (i) ASCII: It returns the decimal representation in the database character set of the first character of string.STRING FUNCTIONS: There are various functions in SQL that can be applied on the string type data.
(ii) UPPER: It returns char. Syntax: Select upper(string/column_name) from <table_name>.

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. Syntax: select lpad(fieldnames) from tablename.PRACTICAL FILE OF RDBMS
(iv) LPAD & RPAD: What this function does is that it fills up the extra space in the field with the padding either from the left or from the right.

format) from <table_name>. then n is converted to a VARCHAR2 value exactly long enough to hold its significant digits. Syntax: Select to_char(value. The value n can be of type NUMBER. If you omit fmt.PRACTICAL FILE OF RDBMS
--CONVERSION FUNCTIONS: (i) To_Char: TO_CHAR (number) converts n to a value of VARCHAR2 datatype. DATE. using the optional number format fmt. BINARY_FLOAT.
(ii) To_Number: It is used to convert character to number datatype. Syntax: Select to_number(µvalue¶) from <table_name>.
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. or BINARY_DOUBLE.

Syntax: Select to_date(µdate¶.PRACTICAL FILE OF RDBMS
(iii) To_Date: It converts a character field to a date field. µformat¶) from <table_name>.
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. was added to SQL because aggregate functions (like SUM) return the aggregate of all column values every time they are called.PRACTICAL FILE OF RDBMS
GROUP BY CLAUSE: GROUP BY. Syntax: SELECT column1. and without the GROUP BY function it was impossible to find the sum for each individual group of column values..<aggregate function>(column2) FROM <table_name> GROUP BY <column1>.
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.... it would be impossible to test for result conditions. was added to SQL because the WHERE keyword could not be used against aggregate functions (like SUM). Syntax: SELECT column1.<aggregate function>(column) FROM table GROUP BY column1 HAVING <aggregate function> condition. and without HAVING.
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.PRACTICAL FILE OF RDBMS
HAVING CLAUSE: HAVING.

keyfield> = <second_table. -. If there are rows in Employees that do not have matches in Orders. <column2>. y LEFT OUTER JOIN
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. <column3> FROM <first_table> INNER JOIN second_table ON <first_table.PRACTICAL FILE OF RDBMS
JOINS: Sometimes we have to select data from two or more tables to make our result complete. We have to perform a join.It displays all the rows of first table or second table or both depending on left outer join .
--Outer Join: Outer join uses two tables to extract the data .right outer join or full outer join. those rows will not be listed. Syntax: SELECT <column1>.keyfield>.INNER JOIN: The INNER JOIN returns all rows from both tables where there is a match.

<column3> FROM <first_table> LEFT JOIN second_table ON <first_table.keyfield>.keyfield> =
<second_table.keyfield>.keyfield>
<second_table. Syntax: SELECT <cloumn1>. ON <column3> FROM =
<first_table>RIGHT
second_table
<first_table.
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.PRACTICAL FILE OF RDBMS
It displays all the rows of the first table of the join. Syntax: SELECT <cloumn1>. <column2>.
y RIGHT OUTER JOIN: It displays all the rows of the second table of the join. JOIN <column2>.

PRACTICAL FILE OF RDBMS
y FULL OUTER JOIN It displays all the rows of the first table and second table of the join.
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. JOIN second_table <column2>.keyfield>.keyfield>
<second_table. Syntax: SELECT <cloumn1>. ON <column3>FROM =
<first_table>FULL
<first_table.

----INTERSECT: It select the common tuples in both the tables.PRACTICAL FILE OF RDBMS
UNION and INTERSECT operations ----Union: It is used to combine the tuples of two different tables.
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Default constraint d. gross decimal). Consider the following SQL command Create table employee (ecode integer NOT NULL. Different Constraints a. Primary key constraint: This declares a column as the primary key of the table. It is similar to default constraint except that only one column can be specified as primary key. Primary key constraint c.PRACTICAL FILE OF RDBMS
Constraints in SQL A constraint is a condition or check applicable on field or set of fields. Example
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. this means the column can never be empty. Example
b. ename varchar2(9) NOT NULl. Unique constraint: This constraint ensures that no two rows have same value in the specified column(s). If you write the keyword NOT NULL after the data type of a column. Check constraint a. Unique constraint b.

automatically the defined default value inserted in the field. Examples
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. Default constraint: A default value can be specified for a column using the DEFAULT clause.PRACTICAL FILE OF RDBMS
c. When a user does not enter value for the column (having default value).
d. Check constraint: This constraint limits values that can be inserted into a column of a table.

Drop index: It is used to vanish the existing index. The users cannot see the indexes.Create Index: It creates a simple index on a table. Query: create index id on studentcse(rollno). Syntax: DROP INDEX index_name ON table_name. Syntax: CREATE INDEX <index_name> ON <table_name> (column_name). -. and each index is given a name. Duplicate values are allowed in simple index. It is possible to create an index on one or more columns of a table.
-.
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. they are just used to speed up queries.PRACTICAL FILE OF RDBMS
INDEXES Indices are created in an existing table to locate rows more quickly and efficiently.

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. a stored procedure. WHERE.. or join statements in a view. The fields in a view are fields from one or more real tables in the database. insert into vw values(&rollno. it allows you to present exactly the data you want to the user.columname2. The database design and structure will NOT be affected by the functions. or from inside another view.«««. to a view. Syntax: Create view <viewname> as select
<columnname1. A view contains rows and columns.PRACTICAL FILE OF RDBMS
VIEWS: A view is a virtual table based on the result-set of a SELECT statement. By adding functions. just like a real table.columname n>From <table_name>.
Using Views A view could be used from inside a query. etc. --CREATE VIEW: This command creates the view of a table. where. Query: create view vw as select rollno. You can add SQL functions.name from studentcse where rollno>300. and JOIN statements to a view and present the data as if the data were coming from a single table.'&name'). joins.

Declaration block (optional) BEGIN -. PL/SQL's syntax strongly resembles that of Ada. A few years later. Each of these is made up of the basic PL/SQL unit which is the block. separated by a comma. it was included in the Oracle Database server v7 (as database procedures. one can further append these in round brackets. The key strength of PL/SQL is its tight integration with the Oracle database.)
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.Exception-handling (optional) END /* Sample comment spanning multiple lines. Some other SQL database management systems offer similar extensions to the SQL language. "scale" refers to the number of digits which can follow the decimal point. used in the Oracle database. Blocks take the general form: DECLARE -.PRACTICAL FILE OF RDBMS
INTRODUCTION TO PL/SQL PL/SQL (Procedural Language/Structured Query Language) is Oracle Corporation's proprietary procedural extension to the SQL database language. functions. Basic code structure PL/SQL programs consist of procedures. functions.Program proper EXCEPTION -. and anonymous blocks. and just like Ada compilers of the 1980s the PL/SQL runtime system uses Diana as intermediate representation. packages.S]) := value. PL/SQL is one of three languages embedded in the Oracle Database.. ("Precision" in this context refers to the number of digits which the variable can hold. To specify the (optional) precision(P) and the (optional) scale (S). */ Numeric variables variable_name number(P[. the programmer appends the variable type NUMBER to the name definition. History PL/SQL made its first appearance in Oracle Forms v3. To define a numeric variable. triggers and anonymous blocks) followed by Oracle Reports v2. the other two being SQL and Java..

The TO_DATE function can be used to convert strings to date values. DATETIME. double precision. long. long raw. Oracle provides a number of data types that can store dates (DATE. smallint. using as a definition the second quoted string. integer. the programmer normally appends the variable type VARCHAR2 to the name definition. raw. binary_double. clob. There follows in brackets the maximum number of characters which the variable can store. decimal. however DATE is most commonly used. format_string). Programmers define date variables by appending the datatype code "DATE" to a variable name. TIMESTAMP etc). Other datatypes for character variables include: varchar. dec. blob. To define a character variable. char.
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. real. nchar. nchar2. int. float.PRACTICAL FILE OF RDBMS
A selection of other datatypes for numeric variables would include: binary_float. The function converts the first quoted string into a date. bfile Date variables variable_name date := '01-Jan-2005'. 'NLS_DATE_LANGUAGE =
To convert the dates to strings one uses the function TO_CHAR (date_string. numeric. for example: TO_DATE('31-12-2004'.'dd-mm-yyyy') "or" TO_DATE American') ('31-Dec-2004'.'dd-mon-yyyy'. binary_integer Character variables variable_name varchar2(L) := 'Text'.

PL/SQL is used for Cursors and Triggers .manipulation of data using DML.Advantage of pl/sql over sql is.you can write many sql statements within a pl/sql block.dcl etc. Embeded SQL is used to embed SQL statements in C.. SQL is a structured query language used for various operations such as retrieval..triggers. PL/SQL is programming language used to write various sql statements together.procedures etc.sql writtens querys by using ddl. And also packages and triggers.
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. Java or any other programming languages.DDL statements.
2. We can write cursors for fetching number of records at a time.. In sql querys process at a time where as in plsql it done step by step or recoed by record .One more advantage is subprogramming like procedures and functions..Pascal.where plsql uses cursors. Embedded SQL .. SQL is Structured Query Language used for DDL. 3. Both sql and pl/sql are languages used to acess data with in oracle data base..Cobol.dml..SQL statements are invoked from a host environment like C/C++.DML.PRACTICAL FILE OF RDBMS
Difference between SQL and PL/SQL 1..Foxpro like languages.

PRACTICAL FILE OF RDBMS
PL/SQL Execution Environment The PL/SQL engine. and the PL/SQL and SQL statement executors work together to process the statements within the procedure. which processes PL/SQL program units. The following Oracle products contain a PL/SQL engine:
y y y y y
Oracle server Oracle Forms (Version 3 and later) SQL*Menu (Version 5 and later) Oracle Reports (Version 2 and later) Oracle Graphics (Version 2 and later)
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. When an application calls a procedure stored in the database. Oracle loads the compiled procedure (or package) into the shared pool in the system global area (SGA).
The procedure (or package) is stored in a database. including the Oracle server. is a special component of many Oracle products.

which can be either an anonymous block or another stored procedure. For example.PRACTICAL FILE OF RDBMS
You can call a stored procedure from another PL/SQL block. you can pass anonymous blocks to Oracle from applications developed with these tools:
y y y y y
Oracle precompilers (including user exits) Oracle Call Interfaces (OCIs) SQL*Plus Server Manager Oracle Enterprise Manager
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. Also. you can call a stored procedure from Oracle Forms (Version 3 or later).

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.PRACTICAL FILE OF RDBMS
Write a PL/SQL block to find greatest number among three numbers.

including basic LOOP statements. or by raising an exception. and Cursor FOR loops. END CASE. WHEN 2 THEN sequence_of_statements_2. Looping As a procedural language by definition.PRACTICAL FILE OF RDBMS
CASE statement can be used with predefined selector: CASE x WHEN 1 THEN sequence_of_statements_1.
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. LOOP statements Syntax: LOOP statement1. FOR loops. statement2. Loops can be terminated by using the EXIT keyword. ELSE sequence_of_statements_N. WHILE loops. PL/SQL provides several iteration constructs. END LOOP.

PRACTICAL FILE OF RDBMS
Write a PL/SQL block that display table for entered no using for loop.
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.

. FOR loops Cursor FOR loops FOR RecordIndex IN (SELECT person_code FROM people_table) LOOP DBMS_OUTPUT. END LOOP. Sequential Statements Syntax: GOTO record Where record is place in the PL/SQL to which goto label shift the control of program. END LOOP..do something.PUT_LINE(RecordIndex.PRACTICAL FILE OF RDBMS
WHILE loops Syntax: WHILE LOOP ..
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.person_code)..

A roolback statemet given at the SQL prompt can be used to undo a part of entire transaction. secondly to make change permanent a commit statement has to be given at SQL prompt. 4. SET TRANSACTION.restore database to original since the last COMMIT.PRACTICAL FILE OF RDBMS
TRANSACT-SQL (T-SQL) It is a part of PL/SQL.
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.identifies a point in transaction to which you can later roll back. Oracle treats a series of operators as a single entity. COMMIT. 3.saves work done. ROLLBACK. Rollback [to[savepoint]savepointname].Change transaction options like isolation level and what rollback segment to use. Syntax: Commit. 1. Savepoint savepoint_name. First the changes requested are done. The changes made to the table is a two step process. SAVEPOINT. 2.

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Query: If price of product 10 is less than 4000 then change the price to 4000. The price change is to be than recorded to the table oldprice along with productnumber (pno). date of change of price and oldprice. Before execution
After execution
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2.PRACTICAL FILE OF RDBMS
Query: Write a PL/SQL block of code as following: 1. then check. 3. made to the salary of the person. Update salary of Raman & Teena by 2000 & 1500. Insert a record in employ2 table.000 then undo the update. To see that the total salary does not exceed 20.
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. If total_salary>20.000.

or package. When a query returns multiple rows. First. Moreover. one.PRACTICAL FILE OF RDBMS
Cursors
PL/SQL uses two types of cursors: implicit and explicit. FETCH. including queries that return only one row. PL/SQL declares a cursor implicitly for all SQL data manipulation statements. you can execute FETCH repeatedly until all rows have been retrieved. and CLOSE. one can explicitly declare a cursor to process the rows. Cursor Attribute Values %FOUN %ISOPE %NOTFOU %ROWCOU D N ND NT OPEN before exception FALSE after First FETCH NULL TRUE TRUE TRUE TRUE exception NULL NULL FALSE FALSE exception 0 0 1 1
before NULL after TRUE
Next FETCH(es)
before TRUE after
TRUE
TRUE TRUE TRUE
FALSE FALSE TRUE
data dependent data dependent data dependent
Last FETCH
before TRUE after FALSE
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. When the last row has been processed. which identifies the result set. one can declare a cursor in the declarative part of any PL/SQL block. we initialize the cursor with the OPEN statement. Explicit Cursors The set of rows returned by a query can consist of zero. Then. We use three commands to control a cursor: OPEN. or multiple rows. we release the cursor with the CLOSE statement. depending on how many rows meet your search criteria. subprogram.

Once a cursor is closed.)] [RETURN return_type] IS select_statement. Each fetch retrieves the current row and then advances the cursor to the next row in the result set. parameter]. Fetching with a Cursor The FETCH statement retrieves the rows in the result set one at a time. Closing a Cursor The CLOSE statement disables the cursor. which consists of all rows that meet the query search criteria. we name it and associate it with a specific query using the syntax: CURSOR cursor_name [(parameter[. For cursors declared using the FOR UPDATE clause. and the result set becomes undefined.PRACTICAL FILE OF RDBMS
CLOSE before FALSE after TRUE TRUE exception data dependent exception
exception FALSE
Declaring a Cursor When we declare a cursor. we can reopen it.. each formal parameter in the cursor declaration must have a corresponding actual parameter in the OPEN statement.
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. where return_type must represent a record or a row in a database table. and parameter stands for the following syntax: cursor_parameter_name [IN] datatype [{:= | DEFAULT} expression] Opening a Cursor Opening the cursor executes the query and identifies the result set. Unless we want to accept default values. Passing Cursor Parameters We use the OPEN statement to pass parameters to a cursor. the OPEN statement also locks those rows..

you can use cursor attributes to get information about the most recently executed SQL statement Using Cursor Attributes Each cursor or cursor variable has four attributes: 1) 2) 3) 4) %FOUND %ISOPEN %NOTFOUND %ROWCOUNT. FETCH. You can use cursor attributes in procedural statements but not in SQL statements
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. Although we cannot use the OPEN. But. and CLOSE statements to control the SQL cursor. FETCH. these attributes return useful information about the execution of a data manipulation statement.PRACTICAL FILE OF RDBMS
Implicit Cursors Oracle implicitly opens a cursor to process each SQL statement not associated with an explicitly declared cursor. Oracle implicitly opens a cursor to process each SQL statement not associated with an explicitly declared cursor.
When appended to the cursor or cursor variable. we can use cursor attributes to get information about the most recently executed SQL statement. We can refer to the most recent implicit cursor as the SQL cursor. PL/SQL lets you refer to the most recent implicit cursor as the SQL cursor. and CLOSE statements to control the SQL cursor. You cannot use the OPEN.

%NOTFOUND yields TRUE if an INSERT. .(i. the implicit cursor attributes yield null the implicit cursor attributes are referred by preceding the implicit cursor attribute with cursor name. %FOUND yields FALSE. %FOUND yields NULL. As a result. or DELETE statement affected no rows. SQL%FOUND Until a SQL data manipulation statement is executed. SQL%ROWCOUNT %ROWCOUNT yields the number of rows affected by an INSERT. UPDATE. %FOUND yields TRUE if an INSERT. or DELETE statement. SQL%NOTFOUND %NOTFOUND is the logical opposite of %FOUND. you use %FOUND to insert a row if a delete succeeds: DELETE FROM emp WHERE empno = my_empno.. %ROWCOUNT
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.e sql). the values of the cursor attributes always refer to the most recently executed sql statement. or DELETE statement affected one or more rows. UPDATE. %ISOPEN always yields FALSE. UPDATE. %NOTFOUND yields FALSE. before oracle opens the sql cursor. In the following example. my_ename. delete. or returned by a SELECT INTO statement.
SQL%ISOPEN Oracle closes the SQL cursor automatically after executing its associated SQL statement.PRACTICAL FILE OF RDBMS
IMPLICIT CURSOR HANDLING implicit cursor attributes return information about the execution of an insert. Otherwise. Otherwise. or a SELECT INTO statement returned one or more rows.). IF SQL%FOUND THEN -. or select into statement. Thereafter. or a SELECT INTO statement returned no rows.delete succeeded INSERT INTO new_emp VALUES (my_empno. update..

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yields 0 if an INSERT. In the following example..more than 10 rows were deleted . you use %ROWCOUNT to take action if more than ten rows have been deleted: DELETE FROM emp WHERE . or DELETE statement affected no rows. or a SELECT INTO statement returned no rows.
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. IF SQL%ROWCOUNT > 10 THEN -.. END IF.. UPDATE..

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Query: Write a PL/SQL block of code to display a message to check whether the record is deleted or not using sql%notfound. Output: Records of employee table before execution:
Program:
Records of employee table after execution:
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.

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.

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Query: Write a PL/SQL block of code to display a message to check whether the record is deleted or not using sql%found. Output: Records of employee table before execution:

Program:

Records of employee table after execution:

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Query: Write a PL/SQL block of code to display a message to give the no of records deleted by a delete statement in PL/SQL block. Output: Records of employee table before execution:

%Type b. Syntax: variable_name <table_name>. b. we need the name of columns and table to which the variable correspond.PRACTICAL FILE OF RDBMS
Implicit cursor handling Kinds of variables: The types of attribute are a. %Rowtype a. %Rowtype: This attribute is used to declare the single variable for various columns in a table.<column_name>%type. %Type: This attribute is used when declaring variables that refer to data base column by using type variable.
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.

ENAME.HRA.TOTAL).PRACTICAL FILE OF RDBMS
Query1: Write PL/SQL code to calculate total salary of employee having Employee number 100. Using %type: Before execution
After execution
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. employee(ENO. the table employee has the following column.BP.DA.

TOTAL).BP. employee(EMPNO. Using %ROWTYPE: Before execution
After execution
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.PRACTICAL FILE OF RDBMS
Query: Write PL/SQL code to calculate total salary of employee having Employee number 100.DA.HRA.ENAME. the table employee has the following column.

Declare a cursor: A cursor is declared in the declare section of a PL/SQL block. Exit from loop. Close a cursor: Syntax: close <cursor_name>. Fetch data from cursor into memory variable: Syntax: fetch <cursor_name> into variable_name. c. Open a cursor: It is use to open cursor explicitly that is by the user.PRACTICAL FILE OF RDBMS
Methods or steps to perform explicit cursor management a. d. Syntax: cursor <cursor_name> is select <statement>.
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. Syntax: open <cursor_name>. b. e.

Query: To display eno. job of employee of department number 10 with the help of cursor for loop. ename. Before execution
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.PRACTICAL FILE OF RDBMS
Cursor for loop Syntax: For <variable_name> in <cursor_name> Loop <SQL statement>.